Error 500 when not including the node_modules folder

Question

LAST UPDATE

It appeared that one my dependencies, not yet 1.0, changed its API between 2 versions. My local version was outdated, and when pushing to Heroku, Heroku downloaded the latest version, with the API change that crashed my app.

CONCLUSION : When using libraries not stable yet (that didn't reach 1.0), stick to a specific version.

Thank you guys for trying to help me.

=================

Using Node 0.8.latest, express 3.latest.

One of my route works perfectly locally, but gives me a 500 error when the app is deployed. The error message is very app-specific, but illogic. It's a TypeError, telling me that something (that should be defined) is undefined. To make it work, the only weird solution I found was to remove node_modules from .gitignore and tracking it under git. When pushed on heroku, no error appears and the url just works

It starts to get strange when you know that I DID NOT change any code inside of the node_modules folder. I also compared locally and "heroku"ly installed dependencies by comparing a local npm ls to the list of modules produced when pushing to heroku, since it rebuilds the dependencies because they're .gitignore 'd. I see minor but inexplicable differences on a few packages noted invalid with npm ls . None of this package is in my package.json file, they're dependencies for my package in package.json . Namely, connect is 2.4.4 locally and 2.5.0 on heroku, send is 0.0.4 locally and 0.1.0 on heroku, emitter-compnonent is 0.0.1 locally and 0.0.5 on heroku. The rest is striclty identical.

The other thing to note is that the error stacktrace points a module which has identical versions on both environments and which doesn't depend on nor isn't a dependency for the modules that have different versions. So even the minor dependency differences shouldn't be the cause of the problem.

But then, I can't see where does the problem come from, and I would like to avoid tracking my node_modules files. Or should I ?

UPDATE

Here's my package.json file as per request by Hector Correa

{
  "name": "myapp",
  "version": "0.1.0",
  "dependencies": {
    "express": "3.0.x",
    "mongoose": "3.0.x",
    "superagent": "0.9.x",
    "oauth": "0.9.x",
    "querystring": "0.1.x",
    "consolidate": "~0.4.0",
    "mustache": "~0.6.0",
    "singly": "*",
    "underscore": "~1.4.1"
  },
  "devDependencies": {
    "mocha": "1.4.x",
    "supertest": "0.1.x"
  },
  "engines": {
    "node": "0.8.x",
    "npm": "1.1.x"
  }
}

Answer 1

Below is working example package.json in Heroku

{
    "name": "MyApp"
    , "version": "0.0.1"
    , "dependencies": {
          "express": "3.x.x"
    }
    , "devDependencies": {
        "mocha": "*"
        , "should": "*"
        , "supervisor": "*"
        , "superagent": "*"
        , "request": "*"
    }
    , "engines": {
        "node": "0.8.x"
        , "npm": "1.1.x"
    }
}